There is a need to acquire from road images the information (such as road markings drawn in the center of roads) that is necessary for map data used in car navigation systems and the like. One method of doing so is to take aerial photographs from midair using an aircraft or the like, and to create, by orthorectification of the aerial photographs taken, road images as viewed directly from above. But with the method of taking aerial photographs from midair, if the aerial photographs are taken when vehicles or other obstructions are present on the roads, the aerial photographs will contain vehicles and it is not possible to create road images that are high in precision. Neither is it possible to photograph the road markings painted beneath such obstructions. Even supposing it is possible to depict the road markings (for example S-T-O-P), there will be large error in the distances between the letters, and the images will be difficult to use for map data.
On the other hand, inventions have been made whereby a super wide angle CCD camera is mounted on a vehicle and films the road markings on the road surface (see for example Patent Document 1).
[Patent Document 1]
Japanese Patent Application Publication No. JP-A-2003-123197